Glass capillary viscometers of many sizes and configurations are known in the art, including three basic types—suspended level, reverse flow, and Ostwald-style. Perhaps the most commonly used viscometers are the Ubbelohde viscometer (suspended level) and the Cannon-Fenske Routine (Ostwald-style) viscometer. Such viscometers typically comprise a generally U-shaped tube having a first branch tube with a capillary tube of a precise narrow diameter and a second branch tube having a reservoir or bulb for holding a sample of a fluid whose viscosity is to be measured. The tops of the U-shape of these viscometers permit the devices to be immersed and maintained in a closed-bottom bath of liquid which is thermostatically controlled, while allowing the sample to be manipulated under pressure or vacuum or allowed to free-flow under the influence of gravity in the viscometer. The reservoir enables a sample to be held for repeat testing and allows for accurate temperature control and stabilization of the sample prior to testing or in between multiple tests. The capillary tube includes one or more timing bulbs which define the operational range of the viscometer. An upper timing mark or sensor is located above the timing bulb, and a lower timing mark or sensor is located below the timing bulb. A known volume is contained within the first branch tube between the upper and lower timing marks or sensors. The kinematic viscosity can be determined by measuring the time for the fluid to pass between the two timing marks or sensors and multiplying the measured time by a calibration factor that is dependent on various physical dimensions of the viscometer. In a U-shaped viscometer such as a Ubbelohde or Ostwald-style, a fluid sample must typically be added to the second branch tube and held in the reservoir, which presents difficulties for mechanized sample loading in automated viscometers.
A fourth type of viscometer, an Atlantic viscometer, is a straight tube that breaches both the top and bottom of a thermostatically controlled bath of liquid and can be loaded from the bottom by either suction or pressure. However, an Atlantic tube comprises only the components of the first branch tube of an Ostwald-style viscometer, i.e., the timing bulb, upper and lower timing marks or sensors, and capillary tube. Because an Atlantic tube does not contain a reservoir, the same fluid sample cannot be retained in the tube for repeat testing to improve accuracy or for extended periods of thermal soaking prior to testing.